Hydrogeological conceptual model of the Gateshead Area - Project Groundwater Northumbria

This report has been produced by the British Geological Survey (BGS) on behalf of Project Groundwater Northumbria, the Flood and Coastal Resilience Innovation Programme (FCRIP) project led by Gateshead Council. It uses existing data and information to provide a conceptual understanding of the hydrogeology of the Newcastle-Gateshead area, whilst discussing recent groundwater trends and groundwater flood susceptibility in the area. It also provides information on how historic coal mining may impact the groundwater system. The report shows two schematic cross-sectional diagrams to visually conceptualise groundwater across the area.
The Gateshead - Newcastle Upon Tyne area geology is composed of sandstones, mudstones, siltstones and coals. This results in a multi-layered aquifer system comprising permeable sandstone aquifers separated by low permeability rocks which form aquitards. Thicker and laterally extensive sandstones, which were deposited by river channels during the Carboniferous Period, form channelised, southwest-northeast orientated aquifer units situated at various depths. Aquifer units may be poorly connected or disconnected from one another, resulting in confined aquifers at depth. Fractures within the bedrock, particularly within the sandstones, and major faults such as the Ninety Fathom fault are likely to facilitate groundwater storage and movement.
Complex and often thick superficial deposits overlying the bedrock impact groundwater where recharge and discharge occur. Groundwater recharge and discharge is inhibited where thick, low permeability, clay-rich till is present. There are also buried valleys which contain complex superficial deposits, often forming a series of aquifers and aquitards. Superficial deposits form significant aquifers where they comprise of permeable sands and gravel. These deposits maybe connected to bedrock aquifers, enabling groundwater exchanges between superficial and bedrock aquifers.
Abundant mine workings across the region increase aquifer storage, and potentially form pathways for groundwater flow, connecting separate aquifer units. Since mining has ceased and pumping of mine waters has stopped or reduced in many locations, groundwater levels have risen (recovered) rapidly across most of the area. This recovery results in natural springs being reactivated as well as mine water discharge occurring via adits and old workings.
Groundwater flood risk has increased as a result, particularly in low relief areas (<10 metres above Ordnance Datum (mAOD) including the River Tyne, River Team and River Derwent valleys where groundwater levels are near or at the surface. Groundwater flooding is also possible in higher elevation areas associated with mine water discharge and where bedrock aquifers outcrop at the surface.